Simplified design methods for pipelines subject to transverse and longitudinal soil movements

Abstract

Pipelines are often subjected to transverse and longitudinal movements due to displacements in the ground caused by landslides. As landslide movements develop, pipelines can undergo transverse and longitudinal displacements and the resistance offered by the surrounding soil steadily increases depending on the soil characteristics. This resistance reaches an ultimate as the soil reaches failure and develops plastic strains. Two simple analytical solutions have been developed based on this concept: one for transverse movements and another for longitudinal movements. Nondimensional relationships have been developed and are presented in the form of charts. These charts permit hand calculations and rapid verification of structural design of the pipeline and, thus, assess the integrity of existing pipelines located in areas with ground instability. A knowledge of the soil strength and subgrade modulus is required along with pipeline geometry and pipe stiffness to apply the nondimensional relationships. The soil parameters can be measured in situ or estimated using empirical correlations. Worked examples are given to illustrate the proposed methods and to show how various pipe failure criteria can be included. Key words : pipelines, landslide, transverse and longitudinal movements, design method.